A cipher which uses a different encryption key every time, as long as the message. The key is XOR'ed with the message to render the cipher text which can then be XOR'ed with the same key to get the plain text.

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13
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3answers
973 views

Can I use a one time pad key twice with random plaintext?

I understand the basics of OTP: $|\text{key space}| = |\text{plaintext space}|$ implies perfect security, key reuse destroys this. Cryptanalysis on the $N$-Time Pad for $N > 1$ involves finding ...
30
votes
2answers
25k views

How does one attack a two-time pad (i.e. one time pad with key reuse)?

My question might appear the same as the question Taking advantage of one-time pad key reuse?, but actually I did read all the answers and none of them helped me with the details I need. I am new to ...
3
votes
2answers
347 views

Why not use an algorithm's code rather than data itself for one time pads?

Instead of using actual data for one time pads, what would be different if the code for an algorithm was exchanged so that to acquire the pad one would execute the algorithm and use its output? Why ...
9
votes
4answers
2k views

What is the difference between a stream cipher and a one-time-pad?

A (synchronous) stream cipher is an algorithm which maps some fixed-length key to an arbitrary-length key-stream (i.e. a sequence of bits): $C : \{0,1\}^k \to \{0,1\}^{\infty}$. This key-stream is ...
33
votes
7answers
25k views

Taking advantage of one-time pad key reuse?

Suppose Alice wants to send encryptions (under a one-time pad) of $m_1$ and $m_2$ to Bob over a public channel. Alice and Bob have a shared key $k$; however, both messages are the same length as the ...